Can't they just get rid of the repair system all together? Or add a console command to remove it? I'd rather deal with the almost non-existent critical failure system of Fallout 1 and 2 then the excessive repairs of 3.
I just got done with another in a long series of playthroughs of Fallout 2. Not having to repair weapons was nice, you could get a favorite and stick with it. Guns were rare in the first two games, expensive and hard to come by. Buying a weapon was a major investment - as costly as home improvements or more in Fallout 3. Consequently, you didn't find many weapons in your travels just lying around, but again you didn't need to. (I'm shamed to admit that the first few times I discovered a duplicate of my current weapon, I snatched it up thinking "ooh, I can use this to repair my weapon - wait a minute" and smacked my forehead.)
But I liked the repair mechanic in Fallout 3 - it added to the immersion of survival for me and the theme of decay. It also made the Repair skill worth something. In the first two Fallouts there were probably a dozen or fewer uses for the Repair Skill in the entirety of each game. Now, they could have just removed the skill altogether, but I think those dozen or so uses a game were nice and worth having, but the skill needed something else to do as well. This allowed Bethesda to also make weapons more common and allow you to loot armor as well off your enemies. In Fallout 1 and 2, just because an enemy had something on them, that didn't mean you got it when they died, which was kind of annoying in its own right. Sure, realistically the armor would be shot to hell and useless under normal circumtstances, but what if I shot them in just the head or eyes?
The problems with Repair in Fallout 3, which have been remedied in NV, is that you had to have a duplicate weapon, you could never repair a weapon to full condition unless you had maxed the Repair Skill, and you had to constantly repair weapons to keep them at their max damage potential. With repair kits available and for sale, you can know repair any weapon you want without having to find another one. With the change to the Repair mechanic, you can now always repair a weapon to mint condition as long as you have enough parts and kits, regardless of your skill - it will just take more kits or parts the lower your skill. Also, with the addition of the notch and buffer zone to condition, you no longer have to worry about constant repair to keep a weapon doing max damage - if starting at max condition, it should last for many fights before you begin to see a dip in its damage or stats.
The weapon condition does not make sense, though. A 5.56 round will still have the same energy on target if fired from a new M-16 or one that's been in service for a since Vietnam.
True, I used a 35 year-old M16 for 4 years, I cleaned it several times a week, and it was quite reliable. Though in this case, we would be talking about a weapon that has been in service since the Revolutionary War if we matched time frames.
But regardless, if you don't clean a weapon regularly or maintain it, it may not break or fall apart in your hands, but it will start to jam frequently. You'll start getting more misfires, and the weapon won't be as reliable. Even if you do clean it on a regular basis, years of abuse and the elements will take their toll on the operation of the weapon.
Take service rifles used by recruits in basic training. Now, in the Marines, the recruits are made to pay special attention to their weapons, clean them religiously, and make sure they are always in working order. Regardless of that, these "student rifles" are notoriously unreliable. They taken hits, falls, and abuses over the years. They've gone through multiple owners. Maybe some recruits didn't clean them as well as they should have, and deposits have built up at a microscopic level in the barrel. I imagine some rifles sit in storage at the armory for months or years at a time. The rifles have been in use for decades. All these conditions are similar to what would happen to a weapon in the Fallout universe, and I'm sure not all the owners of a post-apocalyptic weapon would be as fastidious at cleaning it as the Marines are.
Now maybe the solution isn't to have weapon break or do a lot less damage. Maybe the solution is just to make them more unreliable when not maintained or repaired. Frequent jams and misfires, being forced to perform immediate action to fire the weapon again with each magazine. The weapon would never become useless then, but their would be a high incentive to repair them.